This study is devoted to the study of the motor organization of speech by relating speech acoustics to articulatory movements and the underlying control functions. The techniques to accomplish this object include acoustic analysis, fiberoptic viewing, transillumination, x-ray viewing and electromyography of the articulatory structures, especially the tongue, velar port, and larynx. Normal speech motor organization is to be studied in two ways. Speech may be viewed as the output of a system for generating linguistic messages as they are formed by assembling units in varying segmental and suprasegmental contexts, traditionally defined as studies of coarticulation and compensation. Alternatively, speech may be viewed as a skilled motor act, whose organization is revealed by the response of the system to perturbation during ongoing articulation. To parallel normal studies we will investigate three clinical groups; stutterers, the deaf, and those with apraxia of speech, or non-fluent or Broca's aphasia. These latter three groups will be studied from the point of view of speech motor planning.